This specification relates generally to providing recommendations to users and to providing search results in response to search queries. A search engine receives search queries, for example, from one or more users and returns search results responsive to the queries. As another example, the search engine can optionally receive queries from and return search results to a computing resource, such as another search engine.
For example, the search engine can identify resources responsive to a search query, generate search results with information about the documents, and provide the search results in response to the query. Examples of resources include resources, such as web pages, videos, books, and sound files. Other types of search results, for example, direct answers to questions posed by the user, or a summary of information responsive to the user's query, can also be provided.